Will graduate schools in the United States and abroad accept an online college degree

[raycathode]

If the goal is to get into a Harvard graduate school, it really depends on WHICH specific program OP is trying to get into. The criteria for applying to the different graduate/professional schools are all unique, and the individual programs have different rates of acceptance. For the Mid-Career MPA and the "regular" MPA at Kennedy School for example, the acceptance rate is over 50% for both. I think someone on another forum figured out several programs at Divinity School were well over 50%.
GSAS programs are harder to get in. Business School programs are a rung above that. And Law School is another rung higher in selectivity.

I did an alumni directory keyword search for "Big 3" college undergrads. There is a section you can fill in "Non-Harvard degrees" on your alumni profile. It turned up the following results:

1 TESU grad holds a Harvard Dinivity School MDiv.
1 COSC grad holds a Kennedy School MPA.
2 Excelsior grads hold Kennedy School MPAs.
1 Excelsior grad holds a Harvard Graduate School of Design MDS
1 Excelsior grad impressively holds both a GSAS MA and a Harvard Law School JD
1 Excelsior grad holds a Harvard Business School MBA

I found a few WGU faculty/employees but nobody listing a WGU bachelor's as their non-Harvard degree. Note this does not constitute a complete list of every non-Extension school Harvard grad - only the ones who have A. opted to be listed in the directory and B. went through the trouble of filling out their non-Harvard degrees on their profile.

There are likely more that are opted out of being listed or just didn't add in their non-Harvard degrees. The system doesn't auto-populate your entry with previous degrees. You have to fill it out manually. A surprising number of alumni are listed, yet have never logged into the directory.

Like Hogwart said. Where your degree is from is only part of the package. If you made a strong GPA on at least 60 regionally accredited credit hours, score high on the GRE (if applicable) and have a good application package, I think you have a very realistic shot. If an Ivy master's degree is your goal, you can achieve it.