Those two just seem so completely different from each other. Throughout the series you see how they have a different set of values and beliefs (as opposite as you can get), they have different styles, different opposing opinions and are just opposite of each other in every way. In the end, they are great friends and their friendship and weird commonalities (when they are both dating The Senator) develops into a bond that really can't be explained unless you watch the entire series.
You can just see the weird relationship they have from Oscar's facial expression.
Here is where they are stalking the senator trying to figure out if he is dating another man.
In the end the thing I love most about Oscar and Angela's quirky relationship is that they don't really give up on each other. Oscar is there for Angela when she needs him, and Angela accepts his help. Angela, although she is hurt after her divorce, trusts Oscar enough to tell him her deepest secret.
I think that is the beauty the writers of The Office came up with, they have these beautiful relationships that can teach you deep meanings about your own relationships and provide you insights you may not have originally though of.
If you haven't watched all of the office yet, go check it out. The entire series is on Netflix.