B767 Technician reported that engine oil cap was unsecured after servicing the engine causing a low oil pressure indication in flight.

Narrative

I was part of a crew that was assigned a service check on a B767-300. It was my role to service the aircraft engines. I relayed the information of the quarts of oil required in engines 1 and 2 and after I completed the task my partner input that information into the maintenance log along with the required WAI (Wing Anti Ice) inspection. To my knowledge he has submitted a report. During the oil servicing of the second of the two engines another plane I was assigned to work arrived at the neighboring gate. At the moment I felt the 'need' to complete the task quickly and get to the gate for fear of being late.I was recently informed that I had left the oil cap unsecured on the #1 engine and it arrived in ZZZ with low oil pressure. I realize I had let myself become distracted and I failed in being diligent in completing the task at hand before moving on. I understand I had complacency in this task as I did not retrace my steps to verify that I had secured the oil cap. I believe that if I would have just slowed down and taken one thing at a time this event would have been avoided. During this time there is added pressure with the increase in flight volume; but I know that I must not let that affect the quality of work I perform; and I must take time to verify the work I perform for the safety of flight.