Entrepreneurial Orientation can definitely be taken as a manifestation of individual behavior. Since all people cannot be risk taker, innovative and proactive. To have these traits the person must have individual orientation which is the case of individual difference and hence individual behaviour. To measure these dimensions of individual behaviour your may assess them one by one through different sales available or you may devise your own instrument. Later-on through their cumulative effect, orientation can be gauged.   

Yes, Entrepreneurial Orientation can considered as Individual Behavior in Organizational Context, but has unique distinction from others such as

Peter F. Drucker's (1985) "Innovation and Entrepreneurship" is a good book where he links innovation to entrepreneurial activities of organizational management, key causes of the shifts in advances in ways of doing things. He concentrates a lot on Say's and Schumpeter's ideas to blend them with his own. The first two chapters focus much on individual behaviors as they are related to the entrepreneurial tasks of economic swarms of innovations (what Schumpeter made famous as "creative destruction") within the framework of organizational management decision making processes.

I would summarize Drucker's (1985) view as promoting the idea that modern managers of business organizations are entrepreneurs--or at least it is their main task to be entrepreneurial in their innovative actions. 

May this literatures can help you

Saeed, S., Yousafzai, S., & Engelen, A. (2014). On cultural and economic contingencies of the entrepreneurial orientation-performance relationship. Entrepreneurship Theory and Practice , 38 (4), 255-290.

Covin, J., & Miller, D. (2014). International entrepreneurial orientation: conceptual consideration, research themes, measurement issues, and future research directions. Entrepreneurship Theory and Practices , 38 (1), 11-44.

Alvarez et al (2014) Realism in the study of entrepreneurship. Academy of Management Review 39(2), 227-233

Pratono and Mahmood (2013) Social Capital and Firm Performance: Moderating Effect of Environmental Turbulence, Asian Social Science, 10(19), 56-68

Pratono and Mahmood (2014) Mediating effect of marketing capability and reward philosophy in the relationship between entrepreneurial orientation and firm performance, Journal of Global Entrepreneurship Research 5(5) 1-12

Miller (1983) , who appears to offer the earliest operationaliztion of the entrepreneurial orientation concept:

Entrepreneurial firm as one that "engages in product marketing innovations, undertakes somewhat risky ventures, and is first to come up with proactive innovations, beating competitors to the punch.

The dimensions of Entrepreneurial Orientation may not be taken as a measure for individual behavior for employees. As the scale has been validated for EO.

The EO concept has also been used for firm unit level, and this level is consistent with classical economics in which the individual entrepreneur is regarded as a firm.

this question is relevant to the aspects of Intra-preneurship. Obviously answer can be found from the question itself.

Using the EO scale, it may be useful to measure individual employee's perception of the entrepreneurial orientation of their strategic business unit or the organization as a whole. You could then use these individual perceptions as a correlate of employee willingness/reluctance to adopt.

check this up. it might help you

A recent study explored individual-level measures of risk aversion and proactive personality and their link to entrepreneurial motivation:

Chan, K.-Y., Uy, M. A., Chernyshenko, O. S., Ho, M.-H. R., & Sam, Y.-L. (2015). Personality and entrepreneurial, professional and leadership motivations. Personality and Individual Differences, 77, 161–166. doi: http://dx.doi.org/10.1016/j.paid.2014.12.063

Another relevant paper explores the mediating role of entrepreneurial alertness with respect to outcomes of proactive personality:

Uy, M. A., Chan, K.-Y., Sam, Y. L., Ho, M.-H. R., & Chernyshenko, O. S. (2015). Proactivity, adaptability and boundaryless career attitudes: The mediating role of entrepreneurial alertness. Journal of Vocational Behavior, 115–123. doi: 10.1016/j.jvb.2014.11.005

Individual behavior reflects individual's characteristics such as maintenance of good relationship, drive to achieve success through hard work, calculated risk taking, tolerance of failures, viewing obstacles as opportunities, honesty and integrity. Individual possessing said characteristics, certainly has entrepreneurial orientation. The individual's positive characteristics, nurtured in conducive organizational culture is likely to trigger the individual's creative potential for innovation. This will be further enhanced through organizational agility and absorptive capacity.  

Frese from National University of Singapore has done some seminal work in the area of individual differences and entrepreneurship - http://bizfaculty.nus.edu/faculty-profiles/229-michael

I think so. See the following article:

"Entrepreneurial orientation: a psychological model of success among southern african Small business owners",

Krauss, Stefanie I.; Frese, Michael; Friedrich, Christian; Unger, Jens M.

European Journal of Work and Organizational Psychology Volume 14, Issue 3, 2005

(http://bizfaculty.nus.edu/media_rp/publications/7Fm3B1422891637.pdf).

Hope it could be useful.

The following paper describes the entrepreneurial behaviour of managers, its antecedents & consequences. While this is not exactly what you want, I do think it is an important paper in your area: 

Kuratko, D. F., Ireland, R. D. Covin, J. G. & Hornsby, J. S. (2005). A model of middle-level managers' entrepreneurial behaviour. Entrepreneurship Theory & Practice. November Issue. 699-716.