When we use the phrase "put on the back burner," we mean that something has been postponed, delayed, or ignored. The antonyms for this phrase can vary depending on the context, but some possible options include "prioritize," "accelerate," "focus," "expedite," "fast-track," and "address immediately." These alternatives all suggest taking action instead of putting something aside. For example, if you have a project that you've been meaning to work on but haven't had time for, you could prioritize it by scheduling time in your calendar or accelerating the pace at which you work on it. The bottom line is that the opposite of putting something on the back burner is taking action and moving forward.